Merck and Co Inc. is advancing its push into cancer medicine, announcing three collaborations that will investigate combining its experimental drug MK-3475 with therapies developed by rival drugmakers.

Merck's agreements will explore using MK-3475, a clinical drug designed to fight cancer by unleashing the body's immune system, in combination regimens with complementary products made by Amgen Inc., Incyte Corp. and Pfizer Inc. Financial terms of the deals were not disclosed.

Merck has high hopes for MK-3475, part of a class of drugs known as anti-PD-1 immunotherapies, which work by releasing a brake on the patient's immune system, enabling it to better recognize and attack tumors. MK-3475 is in late-stage trials to treat melanoma, or skin cancer, and potentially more cancers.

Immunotherapies in general — treatments that fight cancer by fine-tuning the body's immune response — represent a growing area of research and potentially lucrative field of drugs for pharmaceutical companies looking to rebuild their pipelines with effective, new products.

Merck Research Laboratories President Roger Perlmutter said the company plans to explore using MK-3475 both as a standalone drug and in combination with others.

Planned investigations include:

Merck will evaluate MK-3475 in clinical studies with Pfizer's drug axtinib, sold under the brand name Inlyta, in patients with renal cell carcinoma, a type of kidney cancer. Separately, Merck will evaluate MK-3475 with Pfizer's investigational drug, PF-2566, being developed to treat multiple cancer types.

Merck will collaborate with Incyte on clinical study to evaluate using MK-3475 in combination with an immunotherapy identified as INCB24360 to treat patients with advanced metastatic cancers, or cancers that spread to other parts of the body, including non-small cell lung cancer.

Merck and Amgen will evaluate MK-3475 in combination with Amgen's investigational immunotherapy called talimogene laherparepvec in a clinical study in melanoma patients.